Simplify the following expression: $\sqrt{13} + \sqrt{117}$
Explanation: First, try to factor any perfect squares out of the radicals. $= \sqrt{13} + \sqrt{117}$ $= \sqrt{13} + \sqrt{9 \cdot 13}$ Separate the radicals and simplify. $= \sqrt{13} + \sqrt{9} \cdot \sqrt{13}$ $= \sqrt{13} + 3\sqrt{13}$ Finally, simplify by combining the terms. $= ( 1 + 3 )\sqrt{13} = 4\sqrt{13}$